An adjustable nozzle comprising a nozzle body with an inlet, an outlet and a flow chamber having a smooth bore extending between the inlet and the outlet. For this purpose, in some illustrative embodiments, an adhesion layer including a metal and at least one non-metal species may be used, such as titanium oxide, in combination with further metal-containing materials, such as titanium, vanadium and gold. The tube controls the amount of feed by having its lower, angled end contained within a feeding tube that is moveable by the individual sow to discharge the feed only when the sow applies a force to the feeding tube.